During structural vibration analysis such as modal and similar analyses, an accelerometer may be mounted on a test structure, and the method of mounting the accelerometer is one of the most critical points in obtaining accurate results. The preferred mounting is by a threaded stud which is secured to the test structure and it is in turn typically received within a threaded aperture within the accelerometer assembly. The portion of the accelerometer about the threaded aperture is typically a flat, smooth surface and prior to threading the accelerometer onto the test structure, a thin film of silicon grease or the like is applied so that there is firm contact between the accelerometer and the test structure. This form of mounting requires a tapped hole in the test structure which may not always be feasible or desired. Also, it should be noted that during a modal analysis test, it may also be required to move the accelerometer to another location on the same structure in order to measure one or more of the structures modes. This necessitates that additional holes must be tapped.
Commonly used alternative and preferred mounting methods include bees-wax, synthetic waxes and adhesives (epoxies). The frequency response of the accelerometer when mounted in this manner is somewhat degraded, but is usually acceptable. It should also be observed that waxes limit their use to temperatures of 40.degree. C. or less.
A permanent magnet is the simplest method when the location to be measured is a flat ferro-magnetic surface. Typically, the magnet is carried by an adapter which is provided with a stud opposite that surface which is to be attached to the structure the accelerometer then being screwed onto the magnet. As the mass of the accelerometer will then be substantially increased, it can therefore only be used for relatively stiff and large objects without affecting the results. Additionally, when adding a magnet to an accelerometer or even when adding an adhesive mounting base, it is necessary to recalibrate the accelerometer assembly due to changes in the mass and mounting.